Android Police has uncovered evidence of android 4.3 in the works, most likely to be announced at I/O next month.

Now I have an Xperia Z which was promised android 4.2.2 last month and i'm thinking now that maybe thats been delayed in favor of 4.3. Its a long shot but it would be nice

In the files Android Police discovered Nexus 4 and Nexus 7 were found so expect 4.3 for those devices shortly after I/O